JP4188361B2 - Automotive pulse radar equipment - Google Patents

Description

  The present invention relates to an in-vehicle pulse radar device that is mounted on an automobile and that measures inter-vehicle distance, relative speed, and the like with surrounding vehicles, and is useful for inter-vehicle distance control, collision damage reduction, and the like.

  Conventionally, in such an on-vehicle pulse radar device, a millimeter wave of 76 GHz band is used as a transmission radio wave. In general, it is difficult to ensure isolation between elements or lines between the high-frequency waves. Therefore, there is a problem in that a transmission pulse wave is directly superimposed on a reception circuit, causing saturation of the reception circuit and hindering an appropriate detection operation. It was.

  To solve such a problem, a radar apparatus that avoids superimposition of a transmission signal on a reception signal has already been proposed (for example, see Patent Document 1). In this radar apparatus, a frequency modulation control signal is input to a voltage controlled oscillator, and a frequency-modulated transmission signal is supplied to a transmission / reception antenna via an antenna sharing unit and transmitted as a radio wave toward a target object. The transmitted radio wave is reflected by the target object and received by the transmitting / receiving antenna. The received reception signal is mixed with the transmission signal output from the voltage controlled oscillator by a mixer to output a beat signal. Hereinafter, the method for calculating the distance from the beat signal to the target object and the like is the same as that of a general FMCW radar, and thus detailed description thereof is omitted.

  In a conventional radar apparatus, transmission and reception are performed in a time division manner in order to avoid the superimposition of the transmission signal described above on the reception signal. A transmission side switch is installed between the voltage controlled oscillator and the antenna sharing means, and a reception side switch is installed between the antenna sharing means and the mixer. The transmission side switch is controlled by a transmission / reception control oscillator. The reception side switch is controlled by the inverter so that the transmission side switch is turned off when the transmission side switch is on (during transmission) and the transmission side switch is turned on when the transmission side switch is off (during reception).

  At this time, the reception signal is received after a delay time Td = 2R / c (c is the speed of light) corresponding to the distance R from the target object from the transmission pulse wave generated by the transmission side switch. Actually, due to the action of the reception side switch, the reception period of the reception signal when the transmission side switch is on is not received as a reception signal, and the reception signal is observed only during the delay time after the transmission side switch is turned off. . As described above, the target object is detected so that the transmission signal is not superimposed upon reception.

Japanese Patent Laid-Open No. 9-243738

  However, when the circuit is actually configured with the above-described conventional radar device, switching noise due to the effect of charging / discharging inside the switch element occurs when the receiving side switch is turned on / off, and in particular, the target from a short distance. The reception signal corresponding to the object has a problem in that the period during which the reception signal is observed is disturbed, and the short-range detection performance is deteriorated or cannot be detected.

  The present invention has been made in view of the above problems, and does not impose unnecessary restrictions on the isolation inside the circuit, and can detect a target object at a short distance even under the influence of switching noise generated from a switch element. It is an object of the present invention to provide an in-vehicle pulse radar device that can be used.

The in-vehicle pulse radar device according to the present invention divides a transmission signal into a transmission pulse wave by dividing the transmission signal by a predetermined on time and off time, and transmits the transmission pulse wave from a transmission antenna toward a target object. An in-vehicle pulse radar device that receives a reflected signal by a receiving antenna and calculates a distance to a target object based on a delay time between the transmission pulse wave and the received signal received by the receiving antenna In, the reception control means for controlling the passage and blocking of the reception signal in synchronization with the transmission pulse wave, the mixing means for mixing the transmission signal and the reception signal, and the reception signal output via the mixing means the falling of the pulse waveform, the noise generated by the control of the reception control means, a shaping means for shaping to delay the passage of the reception control means receives the signal Delayed a predetermined time from the beginning is characterized in that a sampling means for sampling a received signal from the shaping means.

  According to the present invention, it is possible to provide a low-cost in-vehicle pulse radar device that does not need to increase the isolation in the circuit unnecessarily, and even if switching noise occurs from the reception control means, It is possible to detect a target object at a short distance without being affected.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of an in-vehicle pulse radar device according to Embodiment 1 of the present invention. The on-vehicle pulse radar device shown in FIG. 1 includes a modulation signal generator 11 that outputs a triangular waveform similar to that of a general FMCW radar as a modulation signal, and a voltage-controlled oscillator that outputs a transmission signal that is frequency-modulated according to the modulation signal. 1 and frequency modulation means for changing the transmission signal so that the frequency increases or decreases with time.

  The on-vehicle pulse radar device includes a transmission-side switch that converts a transmission signal output from the voltage-controlled oscillator 1 into a transmission pulse wave that is ON / OFF controlled in accordance with a pulse control signal generated by the pulse generator 12, and a pulse generator. On / off control is performed in accordance with a pulse control signal via an inverter 15 that inverts the pulse control signal generated in the unit 12 to constitute a reception control means for controlling the passage and blocking of the reception signal in synchronization with the transmission pulse wave. And a receiving side switch 6.

  The on-vehicle pulse radar device supplies the transmission pulse wave via the transmission side switch 5 to the integrated transmission / reception antenna 3 that is used for both transmission and reception, and is received by the transmission / reception antenna 3. A circulator 13 as transmission / reception connection means for passing a signal as a reception signal, a reception signal from the voltage-controlled oscillator 1 and a reception signal input via the circulator 13 are mixed and output as a baseband reception pulse. A mixer 4 and a low-pass filter (denoted as LPF in the drawing) 14 as shaping means for shaping so that a baseband received pulse from the mixer 4 is input and the falling edge is delayed are provided.

  Further, the in-vehicle pulse radar device serves as a sampling means for sampling the received signal with a delay of a predetermined time after the reception side switch 6 as the reception control means starts to pass the received signal with respect to the output from the low-pass filter 14. The A / D converter 18 and the signal sampled by the A / D converter 18 are input, the beat frequency is extracted using FFT (Fast Fourier Transform), and the target object is extracted in the same manner as a general FMCW radar. And a CPU 20 that calculates a distance, a relative speed, and the like and outputs the detection result to an external device. Needless to say, the operation of the modulation signal generator 11 and the pulse generator 12 is controlled by the CPU 20.

  Next, the operation of the on-vehicle pulse radar device shown in FIG. 1 will be described with reference to the timing charts of the signals shown in FIGS. A triangular waveform is output from the modulation signal generator 11 in the same manner as a general FMCW radar, and is input to a voltage controlled oscillator (denoted as VCO in the drawing) 1 as a modulation signal. The voltage-controlled oscillator 1 outputs a transmission signal that is frequency-modulated according to the modulation signal. The transmission signal output from the voltage controlled oscillator 1 is distributed to the transmission side switch 5 and the mixer 4 and input thereto. In the transmission side switch 5, according to the pulse control signal generated in the pulse generation unit 12, it is converted into a transmission pulse wave as shown in FIG. The transmission pulse wave is supplied to the transmission / reception antenna 3 via the circulator 13 and is transmitted as a radio wave toward a target object (not shown).

  The radio wave reflected by the target object is received again by the transmission / reception antenna 3 and input to the mixer 4 via the circulator 13 as a reception signal. In the mixer 4, the transmission signal and the reception signal are mixed, output as a baseband reception pulse, and input to the low-pass filter 14. As shown in FIG. 2C, the baseband received pulse is output from the low-pass filter 14 in a form in which the falling edge is delayed and input to the receiving-side switch 6.

  The reception side switch 6 is controlled via the inverter 15 to operate in the opposite phase to the transmission side switch 5, and the operation shown in FIG. The reception-side switch 6 blocks the waveform portion 16 in FIG. 2C, and passes only the waveform portion 17 in FIG. 2C to the baseband reception pulse and is input to the A / D converter 18. At this time, as in the conventional radar apparatus, switching noise of the reception-side switch 6 is generated as shown in FIG. 2D and is superimposed on the baseband received pulse.

  The A / D converter 18 avoids sampling of the portion disturbed by the switching noise, and after the time until the switching noise converges, at the timing shown in the timing 19 of FIG. Sampling is performed. Here, since the falling edge of the baseband reception pulse is delayed by the low-pass filter 14, the baseband reception pulse can be detected even if sampling is performed after the switching noise has converged.

  The signal sampled by the A / D converter 18 is input to the CPU 20, the beat frequency is extracted using FFT (Fast Fourier Transform), and the distance to the target object, the relative velocity, etc., as in a general FMCW radar. Is calculated, and the detection result is output to an external device (not shown).

  Therefore, according to the first embodiment, it is possible to provide a low-cost in-vehicle pulse radar device that does not need to increase the isolation in the circuit unnecessarily, and switching noise is generated from the reception control means. However, it is possible to satisfactorily detect a target object at a short distance without being affected by it.

  Further, by integrating the transmitting antenna and the receiving antenna, it is possible to provide a small in-vehicle pulse radar device without impairing the design of the automobile.

  In addition, since the circulator 13 is provided, a control signal for performing transmission / reception switching is not necessary, so that the load on the CPU 20 is reduced and more advanced signal processing can be performed.

  Furthermore, since it is possible to measure the distance of the target object with higher accuracy, the inter-vehicle distance control can be more comfortable, and the collision damage reduction operation can be performed more appropriately.

Embodiment 2. FIG.
FIG. 3 is a block diagram showing a configuration of an in-vehicle pulse radar device according to Embodiment 2 of the present invention. In the in-vehicle pulse radar device according to the second embodiment shown in FIG. 3, the transmission side switch 5, the reception side switch 6, the circulator 13 and the inverter 15 in the in-vehicle pulse radar device according to the first embodiment shown in FIG. , Except that the transmission / reception changeover switch 21 is replaced, and other configurations are the same as those of the on-vehicle pulse radar device according to the first embodiment shown in FIG. 1, and the same parts are denoted by the same reference numerals and the description thereof is omitted. To do.

  Next, the operation of the on-vehicle pulse radar device shown in FIG. 3 will be described with reference to timing charts of signals shown in FIGS. 4 (a) to 4 (d). Since the operation until the modulation signal is output from the voltage controlled oscillator 1 is the same as that of the first embodiment, the description thereof is omitted here. The transmission signal output from the voltage controlled oscillator 1 is distributed to the transmission / reception changeover switch 21 and the mixer 4 and input thereto. In the transmission / reception changeover switch 21, in accordance with the pulse control signal generated by the pulse generator 12, it is converted into a transmission pulse wave as shown in FIG. 4A, supplied to the transmission / reception antenna 3, and directed toward a target object (not shown). Transmitted as radio waves.

  The radio wave reflected by the target object is received again by the transmission / reception antenna 3 and input to the mixer 4 via the transmission / reception changeover switch 21 as a reception signal. In the mixer 4, the transmission signal and the reception signal are mixed, output as a baseband reception pulse, and input to the low-pass filter 14. From the low-pass filter 14, a baseband received pulse is output with a falling delay as shown in FIG. 4B, and is input to the A / D converter 18.

  Also in the second embodiment, as in the first embodiment, the switching noise as shown in FIG. 4C is generated and superimposed on the received signal, but the fall is delayed by the low-pass filter 14, and Sampling by the A / D converter 18 is performed at a timing as indicated by 19 in FIG. 4B after the switching noise has converged, so that a baseband received pulse can be detected.

  Since the operation after the output of the A / D converter 18 is input to the CPU 20 is the same as that of the first embodiment, the description thereof is omitted here.

  Therefore, according to the second embodiment, it is possible to omit the transmission control means and the reception control means by sharing the transmission antenna and the reception antenna in the transmission / reception change-over switch 21, thereby reducing cost and size. Can do.

Embodiment 3 FIG.
FIG. 5 is a block diagram showing a configuration of an in-vehicle pulse radar device according to Embodiment 3 of the present invention. In the in-vehicle pulse radar device according to the third embodiment shown in FIG. 5, the circulator 13 as the transmission / reception connection means in the in-vehicle pulse radar device according to the first embodiment shown in FIG. Other configurations are the same as those of the in-vehicle pulse radar device according to the first embodiment shown in FIG. 1, and the same portions are denoted by the same reference numerals and the description thereof is omitted.

  In Embodiment 3, using 90-degree hybrid circuit 22, the output from transmission-side switch 5 is supplied to transmission / reception antenna 3 and the signal received by transmission / reception antenna 3 is input to mixer 4. It can be performed.

  Therefore, according to the third embodiment, the 90-degree hybrid circuit 22 can be configured in the same process as other transmission lines such as a microstrip line, and a necessary component such as ferrite is mounted on the circulator 13. Since it is not necessary, the cost required for assembly can be reduced, and the reliability can be improved.

Embodiment 4 FIG.
FIG. 6 is a block diagram showing a configuration of an in-vehicle pulse radar device according to Embodiment 4 of the present invention. In the in-vehicle pulse radar device according to the fourth embodiment shown in FIG. 6, the modulation signal generator 11 and the voltage controlled oscillator 1 are replaced with the configuration of the in-vehicle pulse radar device according to the first embodiment shown in FIG. And a sampling time control unit 25 that sequentially changes the delay time of the A / D converter 18 as a sampling means when a target object is detected. . The A / D converter 18 has a variable delay time from when the reception-side switch 6 starts to pass the reception signal until the reception signal is sampled. Other configurations are the same as those of the in-vehicle pulse radar device according to the first embodiment shown in FIG. 1, and the same portions are denoted by the same reference numerals and the description thereof is omitted.

  Next, the operation of the on-vehicle pulse radar device shown in FIG. 6 will be described with reference to FIGS. 2A to 2C and waveform diagrams shown in FIG. In FIG. 6, the transmission signal is output from the oscillator 23, distributed to the transmission side switch 5 and the mixer 4, and input respectively. In the transmission side switch 5, according to the pulse control signal generated in the pulse generation unit 12, it is converted into a transmission pulse wave as shown in FIG. The transmission pulse wave is supplied to the transmission / reception antenna 3 via the circulator 13 and is transmitted as a radio wave toward a target object (not shown).

  The radio wave reflected by the target object is received again by the transmission / reception antenna 3 and input to the mixer 4 via the circulator 13 as a reception signal. In the mixer 4, the transmission signal and the reception signal are mixed, output as a baseband reception pulse, and input to the low-pass filter 14. From the low-pass filter 14, the baseband received pulse is output with a falling delay as shown in FIG. 2 (c), and is input to the receiving side switch 6. The reception side switch 6 is controlled via the inverter 15 to operate in the opposite phase to the transmission side switch 5, and the operation shown in FIG. The reception-side switch 6 blocks the waveform portion 16 in FIG. 2C, and passes only the waveform portion 17 in FIG. 2C to the baseband reception pulse and is input to the A / D converter 18.

  In order to avoid sampling the portion disturbed by the switching noise, the A / D converter 18 has a timing as shown by a waveform portion 19 in FIG. Sampling. Here, since the falling edge of the baseband reception pulse is delayed by the low-pass filter 14, the baseband reception pulse can be detected even if sampling is performed after the switching noise has converged.

  The signal sampled by the A / D converter 18 is judged by the CPU 20 for the presence or absence of the target object. Specifically, the presence / absence is determined by determining that the target object exists when the magnitude of the sampled signal exceeds a predetermined threshold.

  Here, the state of sampling in the fourth embodiment will be described again in detail with reference to FIG. In FIG. 7, reference numeral 24 denotes a baseband reception pulse. When the target object is not detected, sampling is performed at timing 19 in FIG. Once the target object is detected, the CPU 20 controls the sampling time control unit 25 to change the sampling time to the timing 26 in FIG. Further, in the next sampling, the timing is changed to the timing 27 in FIG. 7 and sampling is performed.

  In this way, by changing the sequential timing and performing sampling, it is possible to observe the amount of change of the baseband received pulse waveform shaped by the low-pass filter 14 with respect to time. Here, since the time response of the low-pass filter 14 is known, it is possible to measure the time Td required for the radio wave to travel back and forth with the target object by comparing with the amount of change of the observed baseband received pulse waveform with respect to time. It is self-explanatory. Therefore, the distance from the target object can be accurately measured.

  Therefore, according to the fourth embodiment, it is possible to measure the distance of the target object with high accuracy and in a short time without sequentially changing the sampling delay time.

It is a block diagram which shows the structure of the vehicle-mounted pulse radar apparatus which concerns on Embodiment 1 of this invention. It is a wave form diagram of each switch in FIG. 1, a received signal, and switching noise. It is a block diagram which shows the structure of the vehicle-mounted pulse radar apparatus which concerns on Embodiment 2 of this invention. FIG. 2 is a waveform diagram of a transmission / reception selector switch, a reception signal, and switching noise in FIG. It is a block diagram which shows the structure of the vehicle-mounted pulse radar apparatus which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the vehicle-mounted pulse radar apparatus which concerns on Embodiment 4 of this invention. It is a figure which shows the change of the timing of sampling in Embodiment 4 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Voltage control oscillator, 2 Antenna sharing means, 3 Transmission / reception antenna, 4 Mixer, 5 Transmission side switch, 6 Reception side switch, 7 Transmission / reception control oscillator, 8 Inverter, 11 Modulation signal generation part, 12 Pulse generation part, 13 Circulator , 14 Low-pass filter, 15 Inverter, 18 A / D converter, 20 CPU, 21 Transmission / reception changeover switch, 22 90 degree hybrid circuit, 23 Oscillator, 24 Baseband reception pulse, 25 Sampling time control unit.

Claims (7)

The transmission signal is divided into a predetermined on time and off time to be a transmission pulse wave, the transmission pulse wave is transmitted from the transmission antenna toward the target object, and the signal reflected by the target object is received by the reception antenna. In a vehicle-mounted pulse radar device that calculates a distance to a target object based on a delay time between the transmission pulse wave and a reception signal received by the reception antenna,
Reception control means for controlling the passage and blocking of the reception signal in synchronization with the transmission pulse wave;
Mixing means for mixing the transmission signal and the reception signal;
Shaping means for shaping the falling of the pulse waveform of the reception signal output via the mixing means so as to delay with respect to noise generated by the control of the reception control means ;
A vehicle-mounted pulse radar device comprising: sampling means for sampling the received signal from the shaping means after a predetermined time delay after the reception control means starts passing the received signal. The in-vehicle pulse radar device according to claim 1,
The transmission antenna and the reception antenna are integrated transmission / reception antennas for both transmission and reception,
A vehicle-mounted pulse radar device, further comprising transmission / reception connection means for supplying a transmission pulse wave to the transmission / reception antenna and passing a signal received by the transmission / reception antenna as the reception signal. The in-vehicle pulse radar device according to claim 2,
The on-vehicle pulse radar device, wherein the transmission / reception connection means is a circulator. The in-vehicle pulse radar device according to claim 2,
The on-vehicle pulse radar device, wherein the reception control unit and the transmission / reception connection unit are configured by a transmission / reception changeover switch. The in-vehicle pulse radar device according to claim 2,
The on-vehicle pulse radar device, wherein the transmission / reception connection means is a 90-degree hybrid coupler. In the on-vehicle pulse radar device according to any one of claims 1 to 5,
A vehicle-mounted pulse radar device comprising frequency modulation means for changing the transmission signal so that the frequency increases or decreases with time. In the on-vehicle pulse radar device according to any one of claims 1 to 5,
The sampling means is variable in delay time from when the reception control means starts to pass the received signal until the received signal is sampled,
A vehicle-mounted pulse radar device, further comprising sampling time control means for sequentially changing a delay time of the sampling means when a target object is detected.

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